Forming tool for producing an engraved motif on a sheet

ABSTRACT

A forming tool for the production of sheets, more particularly from a thermoplastic synthetic material, is in the form of a roller, a press, or a casting mould, and comprises, upon its outer surface, engraving elements in predetermined spatial relationship with each other. It is to be possible to produce sheets inexpensively with this apparatus, and production tolerances are low. The engraving elements are provided upon the outer surface, which is made of hard material, more particularly metal. The engraving elements project, above the outer surface, to a predetermined height, and the remainder of the outer surface exhibits a predetermined surface structure.

The invention generally relates to an apparatus for the production ofsheets, more particularly from a thermoplastic synthetic material. Morespecifically, the invention relates to a forming tool for use in such anapparatus, being preferably in the form of a roller, a press, or acasting mould, and comprising, upon its outer surface, engravingelements in predetermined spatial relation with each other. Theinvention furthermore relates to a sheet produced by an apparatus ofthis kind, more particularly for a shower-partition.

Described in German Pat. No. 31 35 628 is an apparatus for producing asheet from a synthetic material, the said apparatus comprising, on itsouter surface, elements in the form of depressions. This known apparatusmay also have an otherwise smoothly polished outer surface, so that thefinished sheet will likewise have a smooth surface. The known sheetcomprises bosses projecting from its surface, corresponding to thedepressions in the apparatus, these bosses having the shape of pearls orbeads and looking, to an observer, like drops of water. With sheets ofthis kind, however, problems arise in connection with sealing andfitting them to profiled frames, as required particularly in the case ofshower partitions. These pearl-like bosses, projections or bulgesusually extend about 0.6 mm above the surface of the sheet, so thatsuitable sealing profiles, made of an elastomeric material, havehitherto had to be provided between the profiled frame and the sheet.Obtaining a satisfactory seal, and ensuring a firm seating of the sheetin a profiled frame, results in a comparatively large increase inproduction costs, especially in the case of sheets whose projections andbulges project to different heights from the surface of the sheet. Highsurface pressures arising in the vicinity of the bulges have led todamage. Moreover, the admissible production tolerances in the profiledrail must be watched since, in the worst cases, these add to theabove-mentioned differences in height. Where the tolerances areexcessive, satisfactory sealing and seating cannot be obtained withcertainty.

German OS No. 25 52 547 describes a matrix for a press, the said matrixserving to form the depth-structures in a sheet. The known matrixcomprises a metal body which is coated with a layer of synthetic resin.The outer surface of the forming tool is thus a layer of synthetic resinwhich has little resistance to abrasion and is not very suitable foreffective mass production. The synthetic resin used hardens in atemperature-range of about 130° to 170° C. and is permanently resistantto heat only up to about 200° C. It is a known fact that the processingtemperatures of thermoplastic synthetic materials are considerablyhigher so that the known apparatus cannot therefore be used forsynthetic materials of this kind.

It is an object of the present invention to provide a forming tool bymeans of which sheets can be produced with lens-like areas, or the like,if possible below the surface of the sheet. The tool is inexpensive toproduce and suitable for efficient production of sheets with theabove-mentioned areas being provided, without difficulty, in desiredspatial arrangement. The outer surface of the tool exhibits, in a simplemanner, the desired surface condition. More particularly, it has asurface polished to a high gloss.

It is also an object of the invention to provide a sheet which, apartfrom depressions or cavities with pearl-like designs, comprises thedesired surface finish, and above all a smooth surface is obtained. Itis also possible therewith to produce such sheets inexpensively and inlarge numbers. It is further possible to fit a sheet into a frame madeof profiled rails, and to produce such profiled rails at low cost andwith low production tolerance requirements. It is also possible toobtain firm seating and sealing of the sheet in the aforesaid profiledframe.

In order to accomplish the above objects, the forming tool of theinvention has an outer surface, made of hard material more particularlymetal, from which surface engraving elements project up to apredetermined height, and the said outer surface furthermore has apredetermined surface finish.

The tool according to the invention exhibits the required finishstructure in the outer surface. According to one advantageousembodiment, the engraving elements are arranged upon the outer surfaceonly when the latter already possesses its required finish structureand, above all, when it has been polished to a high surface finish.During production, the outer surface is first of all provided with thenecessary finish structure, after which the engraving elements arefitted. The said engraving elements are secured to the outer surface ina suitable manner, more particularly by welding, soldering, pressing orscrewing into recesses. It is important, in these cases, that the outersurface exhibit the necessary finish structure before the engravingelements are secured. It is a simple matter, therefore, to prepare theouter surface with a surface finish of desired quality. This is ofimportance with a view to obtaining an outer surface polished to a highgloss. In order to ensure reliable attachment of the engraving elements,the latter are preferably screwed into threaded recesses. The height towhich the engraving elements project from the outer surface may bepredetermined, as required. The said recesses can be produced in theouter surface, in the required spatial relationship with each other, atcomparatively low cost.

In one particular embodiment of the invention, the forming tool, in theform of a roller, a press, or a casting mould is obtained by removing atop layer of material while simultaneously leaving engraving elements tostand up a predetermined height from what has now become the outersurface of the tool, the engraving elements having upper end faces whichare provided with structures or decorations, or are profiled, polishedto a high gloss, or are flat, the parts thereof sunk farthest inwardslying, at least approximately, on a level with the second outer surfaceor thereabove. A forming tool of this kind can be produced at aneconomically acceptable cost, the engraving elements or projectionsexhibiting, without much difficulty, the predetermined spatialrelationship with each other. For all configurations, it is importantthat the sheet to be produced by the apparatus exhibit, on the one hand,a specific surface finish structure and, on the other hand, that itexhibit, in the surface, structurally similar water-drops running downthe sheet. According to the invention, removal of the top layer isobtained by etching or some comparable process, the engraving elementsbeing simply left standing.

In one particular embodiment, the upper end faces of the engravingelements present structures, decorations and, more particularly,inwardly directed sinks, the parts thereof reaching farthest into theinterior extending, at the most, as far as the outer surface. The heightof the engraving elements, and the depth of the structures, decorations,or sinks, are matched in such a manner that corresponding structures,decorations, or also concave or convex sinks are formed on the finishedsheet. The bottom surfaces of the said depressions may, withoutdifficulty, also be designed to resemble pearls or drops of water. Theengraving elements may be welded to the outer surface, soldered thereto,or inserted into recesses. In one preferred embodiment, the saidengraving elements are in the form of pins. Hereinafter, therefore, theengraving elements will be referred to as pins, in spite of the factthat other configurations also lie within the scope of the invention. Itshould be pointed out that the forming tool may comprise a plurality ofdifferently shaped pins. Since the pins project from the outer surface,the lenslike areas in the finished sheet are also located below thesurface thereof. According to the invention, the most deeply sunken partis no deeper than the outer surface. Within the scope of this invention,the decorations, structures, and especially the sinks are formed on theupper end faces of the pins by driving or pressing them in with asuitable tool, more particularly a centre-punch, a pressure-ram, or thelike.

In one particular embodiment, where the engraving elements are securedin threaded bores, the length of the thread in each bore is greater thanthe length of the thread on the pin, a part of the cylindrical surfaceof which is pressed into the thread in the bore. While the pin is beingscrewed in, the external thread thereof is first screwed into the threadin the bore until the cylindrical surface adjoining the external threadreaches the thread in the bore. As the pin is screwed farther in, thecylindrical surface is also drawn into the threads in the bore, where itis clinched. This is a particularly simple way of ensuring reliablelocking.

In order to permit simple screwing-in or insertion of the pins, thelatter are initially longer than is necessary with respect to theirfinal height. They can therefore be securely held with tools, with nodanger of damaging the outer surface of the tool when the pins are beingscrewed-in or inserted. After being screwed in, the pin projecting fromthe outer surface is shortened to the required height. The upperend-face of the remaining stub may then be provided with a sink asrequired.

In order to provide sinks in the pins at low production cost, the saidsinks are fitted by driving or pressing them in with a centre-punch, apressure-ram, a rivet-hammer, or the like. The fitting of the sinksrequires extremely little equipment, the required depth of the sinkbeing obtained by predetermining the force required to drive or pressthem in.

According to one particularly practical embodiment, the height of theengraving elements above the surface is 2 mm, preferably between 0.6 and0.8 mm, and/or up to 40% of the thickness of the sheet to be produced.Furthermore, the diameter or width, i.e. their largest cross sectionallinear dimension, must not exceed a maximum of 60 mm, but is preferably20 mm and, more particularly, between 3 and 9 mm. Although the pins arepreferably cylindrical they may, within the scope of the invention, alsobe of other cross-sectional shapes.

The sheet produced by means of the tool according to the inventioncomprises, in its surface which is polished to a high gloss, cavitieswith bottom surfaces arching upwardly in order to form the saidlens-like areas, the part arched farthest up lying, at leastapproximately, in or below the surface of the sheet. Since the outersurface of the tool for producing sheets can easily be polished smooth,before the pins are inserted, the surface of the sheet is therefore alsovery smooth and flat, thus preventing, in a particularly practical way,any unevenness or other irregularity which might impair the surfacequality of the sheet.

Such a sheet is particularly intended for use in shower partitions, theedges of the sheet being held by means of profiled rails and engaging ingrooves therein. The pearl-like or structured areas are located incavities under the surface of the sheet, which therefore rests with itssurface flat against the wall of the groove in the profiled rail, thusensuring the best possible sealing and firm support. Nor do the cavitiesthemselves affect the seal, especially since the width or diameter ofthe above-mentioned pins or engraving elements, and therefore thecavities in the sheet, are matched, according to the invention, with thedepth of the wall of the groove. The width or diameter of the cavity isless than the adjacent wall of the groove. As a result of theabove-mentioned dimensioning of the engraving elements of the tool, thecavities in the sheet have corresponding dimensions. The sheet madeaccording to the invention may be cleaned without difficulty, thusmeeting the requirements of hygiene. The maximal depth of the cavitiesis preferably between 0.06 and 0.08 mm. With cavities of this design,the upwardly arched bottom surface may provide a structure resemblingwater-drops, but the danger of contamination due to deposits of lime orsoap residues is relatively slight.

A description of preferred embodiments of the invention now follows,having reference to the accompanying drawing, wherein:

FIG. 1 is a perspective view of a forming tool in accordance with theinvention;

FIG. 2 is a cross-section, to an enlarged scale, through a portion ofthe surface of the tool according to FIG. 1;

FIG. 3 is a cross-section, similar to that in FIG. 2, but throughanother embodiment of the tool;

FIG. 4 is a perspective view of a shower partition, the door-elements ofwhich comprise sheets with decorative cavities;

FIG. 5 is a cross-section along the line V--V of FIG. 4, the edge of thesheet being inserted into a profiled rail;

FIG. 6 is a diagrammatical representation in elevation, of anarrangement of rollers, one roller being a tool according to FIG. 1.

FIG. 1 shows a forming tool in the shape of a roller 32 comprisingengraving elements 34 in the form of pins 34 which project from theroller cylindrical outer surface 38. Several of such pins 34 areprovided in specific geometrical relationship with each other, so that asheet produced by means of the roller exhibits cavities resembling waterdrops dripping vertically down its surface. Outer surface 38 of roller32 is polished to a high gloss.

FIG. 2 is a cross-sectional view through a top portion of the roller 32and shows one pin 34. The latter projects from the outer surface 38 andcontains a decorative sink or cavity 40 in its upper end face 39 whichis directed radially outwardly. Instead of the sink shown, anotherstructure, decoration, or the like may be provided in the end face 39 asindicated by the dotted lines. Moreover lateral wall 43 of the engravingelement or pin 34 may also be of different contour, as shown by thedotted lines. Section 42, which is sunk radially farthest towards theinterior, is located above the outer surface 38 and in fact, sunkenportion 42 lies, at the most, approximately on a level with outersurface 38. Pin 34 is at predetermined height 44 above outer surface 38.Height 44 is, at the most 40% of the wall thickness of the sheet to beproduced and is usually about 2, preferably between 0.6 and 0.8 mm. Thepart of the pin 34 projecting above outer surface 38 is preferablycylindrical but, within the scope of the invention, it may also have anoval or similar cross-section.

In the vicinity of the outer surface 38, roller 32 is formed with a bore46 having an internal thread 48 of a length 50. External thread 52 ofpin 34 is screwed into bore 46 but length 54 thereof is less than thesaid thread length 50. A small part 56 of the cylindrical outer surfaceof pin 34 is drawn into internal thread 48 in bore 46, and is thusfirmly seated in the latter. It should be remembered that many such pins34 are inserted into bores 46 in smoothly polished outer surface 38.During production, the bores 46 are drilled, at the desired locations,into outer surface 38, the necessary threads 48 also being cut. As maybe gathered from FIG. 1, different pins may also be of differentdimensions. The height of the pins 34 amounts, at the most, to about 0.6to 0.8 mm. In order to avoid damage to the smoothly polished outersurface 38 while pins 34 are being screwed in, the said pins areinitially considerably longer, as indicated by dotted lines 58. A pin 34may be grasped and screwed into the roller 32 with a suitable tool,after which the pin 34 is shortened to the desired height 44. Finally,sink 40 is driven or pressed into the upper end face with a suitabletool.

FIG. 3 shows a cross-section through another embodiment in whichengraving element 34 is solid with the body of the tool 32, beingproduced by removing specific areas of the roller 32. Here again it isessential that part 42 of the said engraving element, which is sunkfarthest towards the interior, be located, at the most, on a level withouter surface 38 of roller 32. It should be pointed out that instead ofthe roller, a press, a casting mould, a matrix, or the like forming toolcan be produced in the manner according to the invention. An initialouter surface layer 36, of which the upper boundary is indicated by thedotted line, is removed in a suitable manner. During this operation,certain areas are left standing to form engraving elements 34. Theroller 32, or generally speaking, the forming tool, exhibits acorrespondingly deeper second outer surface 38, after removal of theinitial surface 36, above which engraving elements 34 project. Thedecorations, structure and, more particularly, the decorative sinks 40are then formed into the upper end faces 39 of engraving elements 34which have been left standing, this operation being effected by drivingor pressing in a suitable tool, more particularly a centre-punch, apressure-ram, or a rivet-hammer. The shape of sinks 40 is predeterminedin the desired manner by the amount of driving or pressing force. Itwill be seen that this makes it possible to predetermine the shape ofthe pearl-like areas, and the bottom surfaces of the cavities in thesheet to be produced.

FIG. 4 is a perspective view of a shower partition consisting of a framemade out of four frame profiles 2 arranged at right angles to eachother. Three door elements 1,3,5 are arranged displaceably along upperhorizontal frame profile 2, guide means in the form of rollers or thelike being provided (not shown). Moving the door elements opens orcloses a passage through the frame to a shower stall or the like, asrequired. Each of the door-elements contains a sheet 6, preferably madeof a thermoplastic synthetic material, in surface 14 of which cavities 8are provided. These sheets are produced with the forming tool 32described above. For greater clarity, cavities 8 are shown enlarged and,to an observer, the motif resembles drops of water. Door elements 1,3,5also contain frames made out of four profiled rails 10 arranged at rightangles to each other, in which sheets 6 are held. Inserted into visiblesurfaces 13 of frame profiles 2 are facing profiles 11. In such a showerpartition, the proposed sheets 6 may be arranged, not only as shown inthe door elements, but also in so-called lateral walls which areconnected, to the left and/or right, to vertical frame profiles 2 inknown fashion. It is precisely in the case of such lateral walls thatproper sealing and firm seating, in every respect, of the sheets isnecessary, so that the escape of water can be safely prevented under allconditions. Sheets manufactured according to the present invention arefurthermore made of a transparent synthetic material. In the case of thesaid lateral walls, the profiled rails provided for the accommodation ofthe sheet 6 are also designed as frame profiles, in order to obtain astable construction which meets static requirements.

FIG. 5 shows, to an enlarted scale, a cross-section of a sheet 6 made,according to the invention, from a thermoplastic synthetic material. Theedge of sheet 6 is inserted into a groove 12 through a sidewall opening16 in a profiled rail 10, surface 14 of sheet 6 bearing directly againstthe walls defining the opening 16. According to the invention, profiledrail 10 is in the form of a clamping profile, i.e. the sheet 6 isclamped between legs 15 with the walls defining the opening 16. The saidsheet comprises cavities 8 which are produced by the pins 34 describedhereinbefore. Each cavity 8 has a depth 18 of between 0.6 and 0.8 mm.Depth 18 amounts, at the most, to 40% of wall-thickness 19 of sheet 6.Bottom surface 20 is arched upwardly toward surface 14, corresponding tothe sink, explained at the beginning hereof, in engraving element 34.The part of bottom surface 20 arched farthest upward projects, at themost as far as surface 14. In looking towards surface 14, cavity 8 maybe either circular or may have an oval or comparable contour. For thepurpose of imitating a drop of water on surface 14, according to thisinvention the width of the cavity may be greatest in the verticaldirection. Cavity 8 has a diameter or largest width 22 of between 3 and9 mm. Thickness 24 of wall 16 of the opening, which bears directlyagainst sheet 6, is greater, according to the invention, than dimension22 or the maximal width of the cavity 8. This ensures reliable sealingin all cases. If this condition were not met, water could passdownwardly over the cavity to bottom 26 of groove 12, and could then runat right angles to the plane of the drawing towards profiled rail 10,emerging at the end thereof. This is prevented by the configurationaccording to the invention.

FIG. 6 is a diagrammatical representation of an arrangement 60 ofrollers in the form of a roller-smoothing apparatus. This arrangementcomprises a total of three rollers, central roller 32 corresponding tothat shown in FIG. 1. Two wide slot nozzles 62,63 of extruders are showndiagrammatically, through which strips of thermoplastic syntheticmaterial are introduced into the roller gaps. Actually, the one extrudernozzle 62 is sufficient according to the invention. Also fed to the saidarrangement of rollers is a strip 64 of textile fabric which is embeddedbetween the said strips of thermoplastic synthetic material. Roller 32comprises greatly enlarged engraving elements 34 for producingdepressions in surface 14. It need not be emphasized that thecontinuously produced strip emerging from the arrangement of rollers onthe upper left hand side of the drawing, after cooling in the usualmanner, may be cut into individual sheets as required. The essentialcharacteristic is the integration of roller 32, made according to theteaching of the invention into an arrangement of rollers in which atleast one wide slot nozzle delivers the thermoplastic material directlyinto a gap between two rollers, and engraving of the surface, with aminimal amount of energy, simultaneously with the production of thestrip from which the sheet is then cut.

I claim:
 1. A forming tool for producing an engraved motif on a sheet ofmaterial, said forming tool comprising a body having an outer surfaceand a plurality of engraving elements of predetermined height projectingoutwardly of said outer surface and distributed on said outer surfaceaccording to a predetermined spacial arrangement, each said engravingelement having an outer face on which is formed an inwardly curveddepression of predetermined depth, the depth of each depression beingless than the height of the engraving element on which the depression isformed.
 2. A forming tool as claimed in claim 1, wherein said engravingelements have a curved outer contour in order to produce drop-likerecesses in said sheet of material.
 3. A forming tool as claimed inclaim 1, wherein said outer surface has a surface finish which is a highgloss polish.
 4. A forming tool as claimed in claim 3, wherein said bodyis formed with threaded bores opening outwardly onto said outer surfaceand said engraving elements are threaded pins screwed into said bores.5. A forming tool as claimed in claim 3, wherein said body is formedwith bores opening outwardly onto said outer surface and said engravingelements are pins welded into said bores.
 6. A forming tool as claimedin claim 3, wherein said body is formed with bores opening outwardlyonto said outer surface and said engraving elements are pins pressedinto said bores.
 7. A forming tool as claimed in claim 4, wherein saidbores are threaded essentially along the full depth thereof, whereinsaid pins are threaded from the free ends thereof along a length shorterthan said full depth of said bores, and wherein said pins are screwedinto said bores with an unthreaded portion thereof, above said shorterthreaded length, being force-threaded into said threaded bores.
 8. Aforming tool as claimed in claim 3, wherein said engraving elements aresolid with said body.
 9. A forming tool as claimed in claim 3, whereineach of said cavities defines, inwardly thereof, a predetermineddecorative design.
 10. A forming tool as claimed in claim 9, whereinsaid decorative design is shaped for the engraving of a water drop. 11.A forming tool as claimed in claim 3, wherein each of said engravingelements projects from said outer surface a distance at most equal to40% of the thickness of a sheet to be engraved.
 12. A forming tool asclaimed in claim 3, wherein each of said engraving elements projectsfrom said outer surface a distance equal to about 2 mm.
 13. A formingtool as claimed in claim 3, wherein each of said engraving elementsprojects from said outer surface a distance equal to between 0.6 to 0.8mm.
 14. A forming tool as claimed in claim 11, wherein said engravingelements have, in cross-section, a major dimension at most equal to 60mm.
 15. A forming tool as claimed in claim 14, wherein said dimension is20 mm.
 16. A forming tool as claimed in claim 14, wherein said dimensionis between 3 and 9 mm.
 17. A forming tool as claimed in claim 3, whereinsaid body is selected from the class consisting of a roll, a press and acasting mould.
 18. A forming tool as claimed in claim 3, wherein saidbody is made of metal.
 19. A forming tool for producing an engravedmotif on a sheet of material, said forming tool comprising:a first roll;a second roll having a plurality of radially outwardly projectingengraving elements of predetermined height distributed on its surfaceaccording to a predetermined spacial arrangement, each said engravingelement having a radially outer face on which is formed an inwarddepression of predetermined depth, said second roll forming with saidfirst roll a first gap for passage of said sheet of material; and athird roll forming with said second roll a second gap for passage ofsaid sheet of material.
 20. A forming tool as claimed in claim 19,wherein said first and third rolls each have a substantially smoothsurface.
 21. A forming tool as claimed in claim 19, wherein said first,second and third rolls are arranged such that a strip of thermoplasticmaterial may be passed through one of said first and second gaps andaround said second roll through an angular range of at least 180° andthence through the other of said first and second gaps and around one ofsaid first and third rolls whereby recesses formed in said thermoplasticmaterial by the engraving elements on said second roll lie on theradially outwardly directed surface of said strip as it passes aroundsaid one of said first and third rolls.
 22. A forming tool as claimed inclaim 21, further comprising means for smoothing the surface of thestrip of thermoplastic material.
 23. A forming tool as claimed in claim21, further comprising means for extruding a second strip ofthermoplastic material and combining and smoothing said strips in saidsecond gap.